Optical and electrical properties of opal carbon replica and effect of pyrolysis

The optical reflection, electrical conductivity, and magnetoconductance of porous opal carbon replicas which have a periodic nanoscale structure have been studied. The temperature dependence of resistivity in green opal carbon replica is different from that in red opal carbon replica. The electrical properties of replica heat treated up to 3000 degrees C are consistent with those of pyrolitic graphite. The periodicity is found to decrease with this heat treatment by scanning electron microscopy and reflection measurements. Due to alkali metal doping, optical reflection spectra of replica with a heat treatment temperature of 2800 degrees C have changed drastically. The occurrence of positive magnetoconductance indicates the existence of quantum effect at low temperature. These results indicate that the electrical and optical properties can be controlled by pyrolysis technique and porous graphite can be obtained. (C) 2000 American Institute of Physics. [S0021-8979(00)08014-2].